Objectives To investigate the endocrine mechanisms mediating the suppression of ovulation and sexual behavior in subordinate female marmosets . Abstract Female common marmosets exhibit specific behavioral and endocrine responses to changes in social status. Socially subordinated females exhibit reduced sexual behavior and hypogonadotropic anovulation. Both conditions are rapidly reversed on removal of female marmosets from subordinate status. However, we have not systemmatically tested female physiological and behavioral responses to experimentally-induced changes in their hormonal environment, while maintaining their subordinate status. Would altering endocrine status alter ovarian and behavioral function? We therefore set out to induce ovulation in four subordinate females, in social groups comprising 4-7 unrelated adult male and female marmosets, and to monitor their ovarian and behavioral responses. Each subordinate was fitted with a backpack jacket housing a miniaturized, battery-powered, computerized infusion pump. The pump dispensed 1ug gonadotropin-releasing hormone(GnRH) subcutaneously every hour, or a saline solution as a control. Plasma progesterone concentrations were monitored twice weekly, and indicated that ovulation was initiated in each GnRH-treated subordinate within two weeks of commencing treatment. Subsequent abdominal laporoscopic examination of GnRH-treated subordinates revealed the presence of two or three corpora lutea on their ovaries, the typical ovulatory compliment found in this species. Despite the ovulatory responses by all GnRH-treated subordinates, they all remained socially subordinate and almost completely sexually inactive. Thus, while hypogonadotropinism was confirmed as the major endocrine cause of anovulation in subordinate female marmosets, suppressed ovarian function was not implicated as a major factor in maintaining subordinate status and sexual inactivity. These studies are further enabling our delineation of the proximate mechanisms regulating reproductive success in female marmosets and the role of the social environment in regulating female fertility in primates. Key words dominance, infertility, sexual behavior, gonadotropin-releasing hormone, progesterone, infusion pump.